Mat 23:36 Verily I say unto you, All these things shall come upon this generation.
Mat 23:37 O Jerusalem, Jerusalem, you who kills the prophets, and stones them who are sent to you, how often would I have gathered your children together, even as a hen gathers her chickens under [her] wings, and you would not!

This is the last time in Matthew that Christ refers to his generation (genea, in Greek). His first describes his generation earlier in Matthew as children who insist that everyone dance to their tune. His favorite adjectives describing of them is "evil and adulterous," which in Greek, is closer to "worthless and cheating." In one previous discussion of his generation, he compares them unfavorably with the people of Nineveh reacting to Jonah, and the queen of Sheba reacting to Solomon. Here, that same idea is extended, comparing them to their forebearers, who killed God's messagers.

This is the first time Christ uses the term translated as "gather together" (episunagô, literally, "collect and bring in"). The next time he uses it (Mat 24:31) to refer specifically to the gathering of the elect. The term has a sense of someone doing work to bring together something for their own use. God is attempting to bring together people to fulfill his purpose for earth, or, people must come together for them to fulfill God's purpose for them.

"Gather" is from episunagô, which means "to collect and bring or carry in." From sunagô, (sullego, sunazo), which means "to bring together," "to collect," and "to gather." Of people, it means "to come together."